Foam products are used for topical applications of drugs and cosmetics. Aerosol products and particularly foams are complicated physical-chemical structures that do not form under arbitrary circumstances. In particular, a special balance between the foam-forming components is important. Slight shifts in the composition may already result in a collapse of the foam; thus, a formulation of per se active substances may not be capable of being formulated as a foam without further provisions.
The inventors of the present invention have developed a series of novel emulsion-based foam formulations. See, for example, commonly assigned, co-pending application WO 2004/037225.
U.S. Pat. No. 6,423,323 describes a foam skin cream, which optionally contains urea and lactic acid. The skin cream formulation is limited to a very specific list of ingredients that are not contemplated in the present invention.
U.S. Pat. No. 4,145,411 describes shaving foam compositions with low levels of mineral oil (0.25-1% by weight) and urea (0.001-0.006% by weight). A shaving foam is, by definition, not breakable and thus cannot readily facilitate topical administration of an active ingredient and especially is not well-suited for topical administration of compositions geared towards skin penetration.